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External Websites
- University of Maryland - Department of Astronomy - The Drake Equation
- Space.com - Drake Equation: Estimating the Odds of Finding E.T.
- NASA Exoplanet Exploration - Are we alone in the universe? Revisiting the Drake equation
- Pennsylvania State University - College of Earth and Mineral Sciences - The Drake Equation
- Academia - Drake Equation for the Multiverse: From the String Landscape to Complex Life
- SETI Institute - Drake Equation
- Astronomical Society of the Pacific - The Drake Equation: 50 Years of Giving Direction to the Scientific Search for Life Beyond Earth
Britannica Websites
Articles from Britannica Encyclopedias for elementary and high school students.
- Drake’s equation - Student Encyclopedia (Ages 11 and up)
verifiedCite
While every effort has been made to follow citation style rules, there may be some discrepancies.Please refer to the appropriate style manual or other sources if you have any questions.
Select Citation Style
Feedback
Thank you for your feedback
Our editors will review what you’ve submitted and determine whether to revise the article.
External Websites
- University of Maryland - Department of Astronomy - The Drake Equation
- Space.com - Drake Equation: Estimating the Odds of Finding E.T.
- NASA Exoplanet Exploration - Are we alone in the universe? Revisiting the Drake equation
- Pennsylvania State University - College of Earth and Mineral Sciences - The Drake Equation
- Academia - Drake Equation for the Multiverse: From the String Landscape to Complex Life
- SETI Institute - Drake Equation
- Astronomical Society of the Pacific - The Drake Equation: 50 Years of Giving Direction to the Scientific Search for Life Beyond Earth
Britannica Websites
Articles from Britannica Encyclopedias for elementary and high school students.
- Drake’s equation - Student Encyclopedia (Ages 11 and up)
Also known as: Green Bank equation
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- Also called:
- Green Bank equation
- On the Web:
- Academia - Drake Equation for the Multiverse: From the String Landscape to Complex Life (Apr. 02, 2024)
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Drake equation, equation that purports to yield the number N of technically advanced civilizations in the Milky Way Galaxy as a function of other astronomical, biological, and psychological factors.
(Read Carl Sagan’s Britannica entry on extraterrestrial life.)
More From Britannicaextraterrestrial life: The Drake equation and extrasolar lifeFormulated in large part by the U.S. astrophysicist Frank Drake, it was first discussed in 1961 at a conference on the “search for extraterrestrial intelligence” (SETI), held at the National Radio Astronomy Observatory in Green Bank, W.Va. The equation states N = R*fpneflfifcL.
The factor R* is the mean rate of star formation in the Galaxy; fp the fraction of stars with planetary systems; ne the number of planets in such systems that are ecologically suitable for the origin of life; fl the fraction of such planets on which life in fact develops; fi the fraction of such planets on which life evolves to an intelligent form; fc the fraction of such worlds in which the intelligent life form invents high technology capable at least of interstellar radio communication; and L, the average lifetime of such advanced civilizations. These numbers are poorly known, and the uncertainty increases progressively with each factor on the right-hand side of the equation. Widely quoted but at best vaguely known values for these factors are: R* = 10/yr, fp = 0.5, ne = 2, fl = 1, fi fc = 0.01, and thus N = L/10. Accordingly, if civilizations characteristically destroy themselves within a decade of achieving radio astronomy, which is taken as a marker of an advanced civilization, then N = l, and there are no other intelligent life forms in the Galaxy with whom terrestrial researchers can communicate. If, on the other hand, it is assumed that one percent of the civilizations learn to live with the technology of mass destruction and themselves, then N = 1,000,000, and the nearest advanced civilization would be on average a few hundred light-years away.
This article was most recently revised and updated by Amy Tikkanen.